Question

(3x-y)^2-(x+3y)^2因式分解

Answer 1

原式=[（3x-y)+(x+3y)]*[(3x-y)-(x+3y)]

=(3x-y+x+3y)*(3x-y-x-3y)

=(4x+2y)*(2x-4y)

=2(2x+y)*2(x-2y)

=4(2x+y)*(x-2y)

=4(2x^2-3xy-2y^2)

=8x^2-12xy-8y^2